The hottest job of the future might be app developer. All you have to do is look at what you're holding in the palm of your hand to figure out why.

“All of us use our cellphones probably more than we should be every day, and that is what is driving the demand for app developers," said Stacy Rapacon, online editor at personal finance website Kiplinger.com, which has identified the best jobs for the future. "More apps mean more people to develop them.”

The median salary for app developers is $100,000, and the industry is expected to grow by 30 percent over the next decade, according to Kiplinger.

Nurse practitioner is the next best job on Kiplinger's list. The median income for nurse practitioners is $103,000, and the field is expected to grow 35 percent between now and 2027.

FILE- Nurse practitioner Juliana Duque works with a patient in Miami. NPs provide much of the same care as doctors, including routine checkups and writing prescriptions.

“The field, in general, is booming because of the aging population," Rapacon said. "Physical therapists, for example, have plenty of patients to work with, especially as people are growing older and health care treatments are improving. Older people who suffer from heart attacks or strokes or other ailments are able to survive those issues and then may need physical therapy or occupational therapy to continue being able to live independently.”

Half of the jobs in the Top 10 — including physician, physician assistant, health services manager and physical therapist — are in the health care field.

That's likely because, for the first time in history, older people are going to outnumber children in the United States. By 2035, 78 million Americans will be over the age of 65, according to the U.S. Census Bureau.

File -- By 2030, 1 in every 5 U.S. residents will be of retirement age, which will fuel the demand for more health care professionals.

Other occupations on the Top 10 Best Jobs of the Future list include financial manager; marketing research analyst (beneficiaries of the big-data boom); computer systems manager (most businesses use computers); and information security analyst (company computers need to be protected from hackers and others).

On the opposite end of the spectrum are the professions that are dying. These include watch repairer (fewer people are wearing time pieces); builder of prefab homes (a shrinking segment of the U.S. housing market); and textile machine operator — but there is an alternative for those currently working in manufacturing.

Workers exchange spools of thread as a robot picks up thread made from recycled plastic bottles at a processing center for a textile company in Yadkinville, North Carolina.

"What’s disappearing are the low-skill jobs," Rapacon said. "So, if there’s a way you can apply more of a human touch to your work, if there’s a way in manufacturing to learn to manage some of the technology that is being put in place in these production processes, then you can still work in those industries and find opportunities."

Other worst jobs for the future include fabric mender (replaced by technology); shoe machine operator (replaced by technology); and movie projectionist (fewer theaters and less demand for people to work in them).

Kiplinger used available data to develop its lists of the best and worst jobs of the future. However, the job market is changing rapidly and the available data on new and emerging industries is limited.

It's always possible that the hottest jobs of the next decade haven't even been invented.